Diabetes Mellitus (DM) is characterized by elevated blood glucose levels (hyperglycemia). It can occur due to impaired secretion or action of the hormone insulin, which is produced by pancreatic beta-cells to promote the entry of glucose into the cells. It is known that hyperglycemia has an important role in the production of reactive oxygen species in all types of DM and that an imbalance of transition metal as Cu and Fe plays a pivotal role in stimulating the oxidative stress. Different levels of some transition metals, as Cu, Fe, Mn, and Zn has been reported comparing diabetic animal models with the control group. An increased Cu status is also described in diabetic patients. Homeostasis of Cu depends on distinct proteins, where Cu(I)-ATPases are important transmembrane proteins for acquisition, active transport, distribution and elimination of Cu ions. In this review we first provide an overview of the literature about the relationship between diabetes and copper, the modulation of Cu(I)-ATPases activity and protein expression in DM, to next discuss the alternative treatments for diabetes using Cu chelation. V C 2017 IUBMB Life, 69(4): [255][256][257][258][259][260][261][262] 2017
Background/Aims: Dopamine (DA) is a natriuretic hormone that inhibits renal sodium reabsorption, being Angiotensin II (Ang II) its powerful counterpart. These two systems work together to maintain sodium homeostasis and consequently, the blood pressure (BP) within normal limits. We hypothesized that L-tyrosine (L-tyr) or L-dihydroxyphenylalanine (L-dopa) could inhibit the Na+/K+-ATPase activity. We also evaluated whether L-tyr treatment modulates Tyrosine Hydroxylase (TH). Methods: Experiments involved cultured LLCPK1 cells treated with L-tyr or L-dopa for 30 minutes a 37°C. In experiments on the effect of Dopa Descarboxylase (DDC) inhibition, cells were pre incubated for 15 minutes with 3-Hydroxybenzylhydrazine dihydrochloride (HBH), and them L-dopa was added for 30 minutes. Na+/K+-ATPase activity was quantified colorimetrically. We used immunoblotting and immunocytochemistry to identify the enzymes TH, DDC and the dopamine receptor D1R in LLCPK1 cells. TH activity was accessed by immunoblotting (increase in the phosphorylation). TH and DDC activities were also evaluated by the modulation of the Na+/K+-ATPase activity, which can be ascribed to the synthesis of dopamine. Results: LLCPK1 cells express the required machinery for DA synthesis: the enzymes TH, and (DDC) as well as its receptor D1R, were detected in control steady state cells. Cells treated with L-tyr or L-dopa showed an inhibition of the basolateral Na+/K+-ATPase activity. We can assume that DA formed in the cytoplasm from L-tyr or L-dopa led to inhibition of the Na+/K+-ATPase activity compared to control. L-tyr treatment increases TH phosphorylation at Ser40 by 100%. HBH, a specific DDC inhibitor; BCH, a LAT2 inhibitor; and Sch 23397, a specific D1R antagonist, totally suppressed the inhibition of Na+/K+-ATPase activity due to L-dopa or L-tyr administration, as indicated in the figures. Conclusion: The results indicate that DA formed mainly from luminal L-tyr or L-dopa uptake by LAT2, can inhibit the Na+/K+-ATPase. In addition, our results showed for the very first time that TH activity is also significantly increased when the cells were exposed to L-tyr.
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